Four-dimensional trend surface analysis is applied to the geochemical data generated on the drill core samples of the nickeliferous lateritic overburden of South Kaliapani mine to understand the distribution of Ni, Co, Fe₂O₃, Cr₂O₃, SiO₂ and Al₂O₃. The distribution can be used to delineate different ore zones which will help in selective mining/removal of overburden, blending and beneficiation of low grade ores depending on the purpose of their use like nickel extraction, development of ferro-nickel and/or ferro-chrome.

View full abstract

K-Ar dating was performed for volcanic rocks from the early Miocene Odose Formation, Fukaura-Ajigasawa area, Aomori Prefecture in northeast Japan to determine the age of the early Miocene transgression, prior to the Nishikurosawa transgression of these area, and to make clear an spatial distribution of marine sediments (>20 Ma) found in the Oga Peninsula, Akita Prefecture.
     The Odose Formation is divided into three members: the Kiyotakizawa Andesite, the Azumagawa Rhyolite and the Kohamadatezawa Andesite Members in ascending order in the Ajigasawa area (Hirayama and Uemura, 1985), which are corresponded to the lower, middle(Sawabe volcanic rock) and upper part in the Fukaura area (Moritani, 1968).
     Preliminary facies analysis of the Sawabe volcanic rock and the upper part of the Kiyotakizawa Andesite Member of the Odose Formation indicates that these volcanic sequences were deposited in the near shore environment, evidenced by the presence of sandstone with hammocky cross stratification and intrusion of spiracle into aa lava flows.
     A high alumina olivine pyroxene andesite of the Sawabe volcanic rock has an age of 20.0±1.0 Ma which coincide with the age of 20.6±2.0 Ma reported by Fukudome et al. (1990), and an alkali olivine basalt from the upper part of the Kiyotakizawa Andesite Member shows 19.4±1.1 Ma.
     Because marine molluscan fossils were found by Hirayama and Uemura (1985) from the middle part of the Kiyotakizawa Andesite Member, the age from the upper part of the member constrains the upper limit a marine sediment age by early Miocene transgression in Ajigasawa area. Furthermore, the result of the present K-Ar age study indicates that the marine sediments in the area are well correlate with the sediments in the Oga Peninsula.

View full abstract

A large number of manganese deposits (dominantly low to medium grade with high iron, phosphorous and silica) occur in the Precambrian Eastern Ghats complex of Andhra Pradesh and Orissa. The manganese ore bands are syngenetic and syntectonic with the metasedimentary country rocks which comprised of khondalite, quartzite and calc-silicate granulite. They have been metamorphosed under granulite facies followed by granitisation, retrograde metamorphism and supergene enrichment. Braunite, bixbyite, jacobsite, hausmannite, vredenburgite, magnetite, hollandite, pyrophanite, together with spessartite, rhodonite represent the primary manganese oxide and silicate minerals. Cryptomelane, romanechite, pyrolusite, goethite, lithiophorite, ramsdellite, birnessite are the secondary minerals which form the matrix for the primary minerals, replace them and are also observed as veins, cavity fillings and interstitial fillings. Goethite, graphite, hematite and pyrite, together with quartz, orthoclase, garnet, diopside, kaolinite and minor amounts of apatite, collophane, gorceixite, sillimanite, plagioclase, zircon, biotite and muscovite are the gangue minerals. Mineral chemistry of different primary and secondary minerals have been described. Phosphorous in the manganese ores of Eastern Ghats complex is present in almost all the minerals but with varying proportions. The abundance of apatite, gorceixite and collophane in the Mn ores is very small. Order of phosphorous content established in this study is primary minerals<pyrolusite<romanechite<cryptomelane<goethite<oxyhydroxides of Fe and Mn. Various processes suitable for removal of phosphorous, iron and silica from the Mn ore are discussed.

View full abstract